1. Field of the Invention
This application concerns data exchange methodologies for computer aided design systems, and in particular boundary representation techniques.
2. Background Information
In an earlier filed patent application, we discussed some of the challenges and drawbacks of computer aided design (CAD) technology employed by engineers, scientists, and mechanical designers. In particular, a significant technical problem for such people is not always the design work they do, but rather the means by which their design work is shared and exchanged with other engineers, scientists, designers, manufacturers, and customers. Simply put, the problem stems from incompatible, or differently modeled CAD file systems.
To solve these challenges, software designers typically approach the problem from one of two ends. For instance, the most common approach is to conform design behavior on the front end. That is, to force the input to parametric feature based design systems (PFBD systems) to conform to standard syntactical structures. This approach is described by J. H. Han et al. in Modeler-Independence Feature Recognition in a Distributed Environment, Computer-Aided Design, G B, Elsevier Science, Ltd. Publishers, B V, Vol. 30, No. 6, pp. 453-463, published May 1, 1998.
Another common approach is to focus on output file types. This approach has been employed in various forms for years by the various CAD systems vendors. IGES and STEP are standard output file types. A specific implementation using such an approach is disclosed in U.S. Pat. No. 5,717,905, by Iwamoto et al. (concerning Bezier-curve data conversion).
Another approach is discussed, albeit briefly, in Y. C. Kao et al., Development of a collaborative CAD/CAM system, Robotics and Computer-Integrated Manufacturing, Elsevier Science, Ltd. Publishers, Vol. 14, 1998, pp. 55-68. While focusing on isolation issues attendant to coediting or collaboration in CAD/CAM design, that is multi-location real-time design, Kao et al. suggest that there are two alternatives for data exchange between different CAD/CAM systems: one is by direct data base conversation and the other is through a neutral data file. Choosing the former, Kao et al. assert that the latter, neutral data exchange formats, do not support collaborative editing. Moreover, Kao et al. provide no details, beyond co-editing of a non-uniform rational B-spline (NURBS) of how such a system might operate in practice on a parameterized feature. Significantly, the data exchange process itself is secondary to the Kao et al. contribution: they are concerned with connectivity and isolation.